In general, crystalline polyolefins are relatively cheap and have excellent mechanical properties and are therefore used for the production of injection molded articles, blow molded articles, films, sheets, fibers, etc. However, mechanical properties of crystalline polyolefins are not deemed sufficient in some uses, and application of crystalline polyolefins has thus been limited. In particular, they are inferior to polystyrene, ABS resins, and polyesters, e.g., polyethylene terephthalate and polybutylene terephthalate, in stiffness characteristics inclusive of stiffness and heat stiffness (the term "stiffness characteristics" will hereinafter include both stiffness and heat stiffness). In order to improve stiffness characteristics of crystalline polyolefins, various nucleating agents have been employed.
Molded articles obtained from crystalline polyolefin compositions containing various conventional nucleating agents have somewhat improved but still have unsatisfactory stiffness characteristics.
JP-A-63-227594 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") discloses a composition comprising a crystalline polyolefin having incorporated therein an aromatic fluorophosphorus compound as an antioxidant and, if desired, a lubricant, e.g., calcium stearate, a nucleating agent, or a filler. However, the reference gives no suggestion about (1) a combined use of lithium stearate or sodium stearate as a lubricant, (2) a combined use of potassium stearate, strontium stearate or barium stearate as a lubricant, and an aliphatic amine, (3) a combined use of an aliphatic dicarboxylic acid alkali metal salt, an aromatic carboxylic acid alkali metal salt or an aluminum aromatic carboxylate as a nucleating agent, and an aliphatic amine, or (4) a combined use of magnesium hydroxide, aluminum hydroxide, magnesium oxide, magnesium carbonate or calcium carbonate as a filler, and an aliphatic amine, still less about an improvement in stiffness characteristics brought about by such combinations.